Contoured battery for implantable medical devices and method of manufacture

ABSTRACT

A battery having an electrode assembly located in a housing that efficiently utilizes the space available in many implantable medical devices is disclosed. The battery housing provides a cover and a shallow case a preferably planar, major bottom portion, an open top to receive the cover opposing the bottom portion, and a plurality of sides being radiused at intersections with each other and with the bottom to allow for the close abutting of other components located within the implantable device while also providing for efficient location of the battery within an arcuate edge of the device. The cover and the shallow case being substantially hermetically sealed by a laser weld technique and an insulator member disposed within the case to provide a barrier to incident laser radiation so that during welding radiation does not impinge upon radiation sensitive component(s) disposed within the case.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/785,113, filed Mar. 5, 2013 entitled “CONTOURED BATTERY FORIMPLANTABLE MEDICAL DEVICES AND METHOD OF MANUFACTURE”, hereinincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of batteries for implantablemedical devices. More particularly, the present invention relates tovolumetrically efficient batteries for implantable medical devices.

BACKGROUND OF THE INVENTION

Implantable medical devices are used to treat patients suffering from avariety of conditions. Examples of implantable medical devices areimplantable pacemakers and implantable cardioverter-defibrillators(ICDs), which are electronic medical devices that monitor the electricalactivity of the heart and provide electrical stimulation to one or moreof the heart chambers, when necessary. For example, a pacemaker sensesan arrhythmia, i.e., a disturbance in heart rhythm, and providesappropriate electrical stimulation pulses, at a controlled rate, toselected chambers of the heart in order to correct the arrhythmia andrestore the proper heart rhythm. The types of arrhythmias that may bedetected and corrected by pacemakers include bradycardias, which areunusually slow heart rates, and certain tachycardias, which areunusually fast heart rates.

Implantable cardioverter-defibrillators (ICDs) also detect arrhythmiasand provide appropriate electrical stimulation pulses to selectedchambers of the heart to correct the abnormal heart rate. In contrast topacemakers, however, an ICD can also provide pulses that are muchstronger and less frequent. This is because ICDs are generally designedto correct fibrillations, which is a rapid, unsynchronized quivering ofone or more heart chambers, and severe tachycardias, where theheartbeats are very fast but coordinated. To correct such arrhythmias,an ICD delivers a low-, moderate-, or high-energy shock to the heart.

Pacemakers and implantable defibrillator devices are preferably designedwith shapes that are easily accepted by the patient's body whileminimizing patient discomfort. As a result, the corners and edges of thedevices are typically designed with generous radii to present a packagehaving smoothly contoured surfaces. It is also desirable to minimize thevolume occupied by the devices as well as their mass to further limitpatient discomfort. As a result, the devices continue to become thinner,smaller, and lighter.

In order to perform their pacing and/or cardioverting-defibrillatingfunctions, pacemakers and ICDs must have an energy source, e.g., atleast one battery. Known high current power sources used in implantabledefibrillator devices employ deep, prismatic, six-sided rectangularsolid shapes in packaging of the electrode assemblies. Examples of suchdeep package shapes can be found in, e.g., U.S. Pat. No. 5,486,215 (Kelmet al.) and U.S. Pat. No. 6,040,082 (Haas et. al.). While theseprismatic cases have proven effective for housing and electricallyinsulating the electrode assemblies, there are volumetric inefficienciesassociated with deep prismatic cases.

One volumetric problem associated with deep prismatic cases is theexcess volumetric size of the implantable medical device caused byplacing these prismatic batteries within the contoured implantablemedical device. As stated above, implantable medical devices arepreferably designed with shapes that are easily accepted by thepatient's body and which also minimize patient discomfort. Therefore,the corners and edges of the devices are typically designed withgenerous radii to present a package having smoothly contoured surfaces.When the deep prismatic battery is placed within the contouredimplantable device, the contours of these devices do not necessarilycorrespond and thus the volume occupied within the implantable devicecannot be optimally minimized to further effectuate patient comfort.

Another volumetric problem associated with deep prismatic cases is theexcess volume within the headspace. In a typical implantable devicebattery the headspace houses the electrode connector tabs, feedthroughpin, insulators, and various other connection components. In typicaldeep battery cases, the battery case has a prismatic top and thendescends downward with possibly curved sides to a bottom. Thus whiledeep cases could provide for slightly contoured sides it could notprovide for contours all throughout the battery case. Thus as shown inFIG. 13, the battery case would have to extend above the electrodeassembly to accommodate the electrode connector tabs, feedthrough pin,etc. This is volumetrically inefficient since all that technically needsto extend from the top of the electrode assembly is the electrodeconnector tabs and the feedthrough pin. This inefficiency is due tomanufacturing limitations, which make it difficult to create severalcurved surfaces in deep battery cases.

Although the use of curved battery cases in implantable devices isknown, they are typically found in devices requiring only low currentdischarge such as pacemakers as described in U.S. Pat. No. 5,549,985 andU.S. Pat. No. 5,500,026. However, these batteries used thin,flat-layered electrodes that do not package efficiently within curvedcases, thus contributing to volumetric inefficiencies. Batteries withcurved cases have been used in connection with the high currentbatteries required for, e.g., implantable defibrillator devices.However, as discussed above, the curvature of these battery cases islimited due to manufacturing limitations associated with deep cases.

For the foregoing reasons, there is a need for a contoured, low profilebattery for implantable medical devices, which allows for shapeflexibility in the design of the battery to match the contours of animplantable device and fit within the available device space thusproviding for a reduction in the volume of the implantable device.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises various embodiments which providesolutions to one or more problems existing in the prior art respectingefficient battery case design for implantable medical devices. Among theproblems in the prior art is the lack of a battery case design for usewith electrode assemblies that can be: (1) efficiently packaged withinan arcuate edge of the implantable device housings, (2) substantiallyreduces the amount of volume utilized within the implantable medicaldevice and (3) provides flexibility in the placement of the feedthroughpin.

Accordingly, it is an object of the invention to provide a batteryhaving a high surface area electrode assembly housed in a case thatefficiently utilizes the space available within many implantable medicaldevices.

Battery housings in embodiments of the invention may include one or moreof the following features: (a) a cover, (b) a shallow case having a(preferably) planar bottom portion, an open top to receive the cover;and at least two sides being radiused at intersections with the bottom,(c) a feedthrough assembly providing electrical communication between atleast one electrode and implantable medical device circuitry, (d) acoupling providing electrical communication between the feedthroughassembly and the at least one electrode, (e) an insulator adjacent tothe cover providing a barrier between an electrode assembly and thecover, (f) an insulator adjacent to the case providing a barrier betweenthe electrode assembly and the case, and (g) a headspace portionextending from a portion of one of the sides.

Batteries in one or more embodiments of the present invention mayinclude one or more of the following features: (a) an electrode assemblyincluding an anode and a cathode, (b) an electrolyte, (c) a batteryhousing enclosing the electrode assembly and within which the electrodeassembly and the electrolyte are disposed, the housing comprising acover, a shallow case having a (preferably) planar bottom portion, anopen top to receive the cover; and a plurality of sides being radiusedat intersections with each other and with the bottom, (d) a headspaceregion extending from a portion of one of the plurality of sides, (e) afeedthrough assembly providing electrical communication between at leastone electrode and implantable medical device circuitry, (f) a couplingproviding electrical communication between the feedthrough assembly andthe at least one electrode, (g) an insulator adjacent to the coverproviding a barrier between an electrode assembly and the cover, (h) andan insulator adjacent to the case providing a barrier between theelectrode assembly and the case.

Implantable defibrillator devices in one or more embodiments of thepresent invention may include one or more of the following features: (a)a device housing comprising at least one arcuate edge, (b) a capacitordisposed within the device housing, (c) a battery disposed within thedevice housing and operatively connected to the capacitor, the batterycomprising an electrode assembly, and an electrolyte (d) a hermeticallysealed battery housing within which the electrode assembly and theelectrolyte are disposed, the housing comprising a cover, a shallow casehaving a (preferably) planar bottom, an open top to receive the cover;and at least two sides being radiused at intersections with the bottomwherein the radiused sides of the battery case nests within one of thearcuate edges of the device housing, (e) a headspace region extendingfrom a portion of one side, and (f) a feedthrough assembly providingelectrical communication between at least one electrode and implantablemedical device circuitry.

Methods of manufacturing batteries for implantable medical devicesaccording to the present invention may include one or more of thefollowing steps: (a) providing a shallow battery case having an openend, a base located opposite the open end, and a plurality of sidesbeing radiused at intersections with each other and the base, (b)inserting an electrode assembly into the battery case, (c) placing acover over the open end of the case, and hermetically sealing the coverto the case, and (d) placing an electrolyte inside the battery case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a battery according to thepresent invention;

FIG. 2 is a bottom profile of a battery case embodiment of the presentinvention;

FIG. 3 is a side profile battery case embodiment of the presentinvention;

FIG.4 is cutaway side profile of several attachment embodiments betweena battery cover and a battery case;

FIG. 5 is a side elevated perspective of a battery case liner of thepresent invention;

FIG. 6 is a front profile of an electrolyte fillport embodiment of thepresent invention;

FIG. 7 is a side elevated perspective of an electrode assemblyembodiment of the present invention;

FIG. 8 is a side elevated perspective of an insulator cup embodiment ofthe present invention;

FIG. 9 is a top profile of a battery cover with a header assembly of thepresent invention;

FIG. 10 is a side profile of a battery cover with a header assembly ofthe present invention;

FIG. 11 is a front profile embodiment of a feedthrough assembly of thepresent invention;

FIG. 12 is a cutaway view of a headspace embodiment showing thefeedthrough pin connection with the coupling;

FIG. 13 is an elevational, exploded pictorial view of the headspace inprior art implantable medical device batteries;

FIG. 14 is an elevated perspective of a headspace insulator embodimentof the present invention;

FIG. 15 is a rear profile perspective of a headspace insulatorembodiment of the present invention;

FIG. 16 is an exploded perspective view of battery insulators andconnector; and

FIG. 17 is an elevated side profile of a battery connector embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description is to be read with reference to thedrawings, in which like elements in different drawings have likereference numerals. The drawings, which are not necessarily to scale,depict selected embodiments and are not intended to limit the scope ofthe invention. Skilled artisans will recognize that the examplesprovided herein have many useful alternatives that fall within the scopeof the claimed invention.

The present invention is not limited to implantable cardioverterdefibrillators and may be employed in many various types of electronicand mechanical devices for treating patient medical conditions such aspacemakers, defibrillators, neurostimulators, and therapeutic substancedelivery pumps. It is to be further understood; moreover, the presentinvention is not limited to high current batteries and may utilized forlow or medium current batteries. For purposes of illustration only,however, the present invention is below described in the context of highcurrent batteries.

As used herein, the term battery (or batteries) include a singleelectrochemical cell or cells. Batteries are volumetrically constrainedsystems in which the components in the case of the battery cannot exceedthe available volume of the battery case. Furthermore, the relativeamounts of some of the components can be important to provide thedesired amount of energy at the desired discharge rates. A discussion ofthe various considerations in designing the electrodes and the desiredvolume of electrolyte needed to accompany them in, for example, alithium/silver vanadium oxide (Li/SVO) battery is discussed in U.S. Pat.No. 5,458,997 (Crespi et al.). Generally, however, the battery mustinclude the electrodes and additional volume for the electrolyterequired to provide a functioning battery.

The present invention is particularly directed to high current batteriesthat at least with respect to ICDs are capable of charging capacitorswith the desired amount of energy, preferably about 20 joules or more,typically about 20 joules to about 40 joules, in the desired amount oftime, preferably about 20 seconds or less, more preferably about 10seconds or less. These values can typically be attained during theuseful life of the battery as well as when the battery is new. As aresult, the batteries must typically deliver up to about 5 amps at about1.5 to about 2.5 volts, in contrast to low rate batteries that aretypically discharged at much lower currents. Furthermore, the preferredbatteries must be able to provide these amounts of energy repeatedly,separated by about 30 seconds or less, more preferably by about 10seconds or less.

With reference to FIG. 1, a preferred battery according to the presentinvention is depicted. Battery 10 is comprised of a battery case 12(FIG. 2), electrode assembly 14, insulator cup 16, battery cover 18,coupling 20, headspace cover 22, feedthrough assembly 24, and batterycase liner 31. The battery case 12 is designed to enclose the electrodeassembly 14 and be hermetically sealed with battery cover 18.

With reference to FIGS. 2 & 3, a bottom and side profile respectively isshown of a battery case. Battery case 12 is comprised of battery space30 which houses electrode assembly 14, headspace 32, fillport 34, whichallows for the input of electrolyte into battery 10, and open end 29.Battery case 12 is preferably generally arcuate in shape where sides 26meet with top 28 of battery case 12. This construction provides a numberof advantages including the ability to accommodate the curved or arcuateends of a preferred coiled electrode assembly 14. As will be more fullydiscussed below, the arcuate sides 26 can also nest within the arcuateedges of an implantable medical device such as an implantable cardiacdefibrillator.

Battery case 12 is preferably made of a medical grade titanium, however,it is contemplated that battery case 12 could be made of almost any typeof material, such as aluminum and stainless steel, as long as thematerial is compatible with the battery's chemistry in order to preventcorrosion. Further, it is contemplated that shallow battery case 12could be manufactured from most any process including but not limited tomachining, casting, stamping, milling, so-called rapid prototypingtechniques (e.g., using an SLA and the like) thermoforming, injectionmolding, vacuum molding, etc., however, case 12 is preferablymanufactured using a shallow drawing process. Headspace 32 housesinsulators and connector tabs, which transfer electrical energy fromelectrode assembly 14 to the implantable medical device circuitry andwill be discussed in more detail below. However, as shown in FIG. 2, asignificant amount of headspace is reduced from prior battery assembliessuch as the one shown in FIG. 13.

With reference again to FIG. 3, lip 27 is utilized to hold battery cover18 in place not allowing cover 18 to drop within battery case 12.Further, lip 27 provides protection to electrode assembly 14 during thewelding process, which is preferably performed by laser welding,however, other methods of attachment are contemplated. For example,resistance welding, brazing, soldering and similar techniques may beemployed and/or adhesive materials may be used to couple the cover 18 tothe case 12. Lip 27 provides a shelf or ledge designed to reduce thelikelihood of, if not completely prevent, a portion of radiation emittedfrom the laser beam from penetrating battery case 12 and damagingradiation sensitive components therein. This would be especially true ifthis shelf were not present and a gap between cover 18 and case 12 werepresent there would exist a large risk that electrode assembly 14 couldbe damaged by a laser penetrating the gap and causing heat damage toelectrode assembly 14.

With reference to FIG. 4, several cutaway side profiles of attachmentembodiments between a battery cover and a battery case are shown. Inprofile A, lip 27 is cut at 90° to provide even more protection duringthe welding process. While more protection is typically desired, the 90°lip 27 of profile A can be difficult to manufacture. In profile B, lip27 is bent outward and then preferably cover 18 is placed overtop andbutt welded to case 12. In profile C, lip 27 is also bent outward,however, in profile C, a crimp 25 is utilized to help prevent a laserbeam from penetrating battery case 12. In profile D, lip 27 iseliminated and the outer edge of cover 18 is bent over before beingwelded to case 12 to help prevent the laser from penetrating case 12during welding. In profile E, the outer edge of case 12 is bent over topof cover 18 before being welded. In profile F, cover 18 simple restsupon the upper edge of case 12 and then is butt welded together. Inprofile G, the upper edge of case 12 is bent slightly inward with cover18 resting upon to be butt welded to case 12. Each of these embodimentsis meant to provide protection to electrode assembly 14 during thewelding process, which is preferably performed by laser welding,however, other methods of attachment are contemplated. Each embodimentis meant to prevent the welding laser beam (represented by the arrow inthe Figure) from penetrating battery case 12 and damaging electrodeassembly 14. Further, the term welding can encompass many types ofattachment such as resistance welding and brazing, however, all weldsare preferably laser welds. It is also contemplated that many types ofattachment could be utilized without departing from the spirit of theinvention.

As discussed above, traditional battery cases were deep cases whereinthe opening to the case was perpendicular to the deepest portion of thebattery. There are two major drawbacks to this traditional design.First, there are manufacturing limitations to the amount of curvature,which can be implemented into the case. Therefore, most cases would havea substantially prismatic case, which, as discussed above, is verylimiting when packaging the case within the implantable medical device.Second, because the headspace exists at the open end of the case, itconsumes an entire side of the case. In contrast to deep cases, batterycase 12 is manufactured using a shallow form process, which allows forcorners of case 12 to be radiused as well as providing for thepossibility of many varying shapes of case 12. By doing so, the volumecase 12 occupies is substantially reduced. Further, because battery case12 can be manufactured with various shapes and contours, a substantialamount of headspace room can be eliminated and thus more volume withinthe implantable medical device can be reduced. The inventors of thepresent invention have found a reduction in excess of on the order ofabout 10%.

With reference to FIG. 5, a battery case liner used to isolate thebattery case from the electrode assembly is shown. Case liner 31 ispreferably comprised of ETFE and has a thickness of 0.013 cm. (0.004inches), however, other thicknesses and types of materials arecontemplated such as polypropylene, silicone rubber, polyurethane,fluoropolymers, and the like. Case liner 31 preferably has substantiallysimilar dimensions to battery case 12 except that case liner 31 wouldhave slightly smaller dimensions so that it can rest inside of batterycase 12. From the case liner's shape as shown in FIG. 5 and the batterycase's shape as shown in FIG. 2, it is clear to one of skill in the arthow case liner 31 would rest within battery case 12. For example, theheadspace area of case liner 31 would line up with headspace 32 ofbattery case 12 except it would be slightly smaller to accommodate forfillport 34.

With reference to FIG. 6, a front profile of the electrolyte fillport isshown with a fillport ball seal and a closing button. Fillport 34 isused to route lithium hexafluoroarsenate electrolyte into battery 10.Although lithium hexafluoroarsenate is preferably used for the presentembodiment, it is contemplated that most any chemical electrolyte couldbe used without departing from the spirit of the invention. Fillport 34is preferably laser welded to battery case 12 and preferably has ahermetic seal to ensure no electrolyte leakage. However, it iscontemplated that fillport 34 could be attached to case 12 in anyfashion, such as any suitable hermetic joint as is known to those ofskill in the art. Fillport 34 is preferably comprised of titanium andhas a diameter of 0.1117 inches at the top and 0.060 inches at thebottom, however, it is fully contemplated that fillport 34 could be mostany thickness or type of electrochemically compatible material. However,for the ease of manufacturing and reliability of the weld, case 12 andfillport 34 are preferably made from the same material.

From the figure it is shown that fillport 34 has an opening 36 in whichto receive an electrolyte injection device that transfers electrolytefrom the device to battery 10 through conduit 38. Further, it is shownthat the upper portion of fillport 34 is tapered so that fillport 34 canrest within an opening in case 12 before fillport 34 is welded to case12. It is of note that the opening in case 12 for fillport 34 does notnecessarily have to be located in headspace 32 and can be locatedanywhere in case 12 or cover 18 without departing from the spirit of theinvention. Once the electrolyte has been injected within battery 10,fillport ball seal 35 is placed within conduit 38 to create a“press-fit” hermetic seal, which prevents any electrolyte from escapingthrough conduit 38. Closing button 37 is then placed over aperture 33and is welded to fillport 34. Closing button 37 is preferably comprisedof medical grade titanium and ball seal 35 is preferably comprised of atitanium alloy of titanium aluminum and vanadium, however, othermaterials and alloys are contemplated as long as they areelectrochemically compatible. It is further shown in the figure thatfillport 34 is tapered from the top to the bottom. This provides formaximum space inside battery 10, further the taper provides a largerupper area for button 37 to be welded to, which allows for button 37 tobe larger and thus easier to handle and weld to fillport 34.

With further reference to FIG. 6, it is shown that fillport 34 extendsentirely from case 12 to cover 18. Since case 12 and cover 18 arepreferably 0.038 cm. (0.015 inches) thick, fillport 34 provides supportby extending from case 12 to cover 18 so that an indentation or dentingdoes not occur during the “press-fit” operation where ball seal 35 ispressed within conduit 38. If fillport 34 did not extend from case 12 tocover 18 there is a risk that denting could occur during the “press-fit”operation due to the thinness of case 12 and cover 18. Further, distalend 39 of fillport 34 is tapered so that electrolyte can freely enterbattery 10. The taper allows conduit 38 to be unobstructed by cover 18and thus the injection of electrolyte occurs more easily.

Other fillport embodiments and locations are contemplated withoutdeparting from the spirit of the invention. One embodiment includes alow profile fillport (e.g., one that does not extend from the case tothe cover) that is located near the corners of case 12 and cover 18. Inthis embodiment, indentation during the “press-fit” is inhibited by thesupport provided by the sides of case 12 (or cover 18) in the corner.Further, this embodiment can be implemented in case 12 or cover 18 aslong as the low profile fillport is placed in a corner of the vesseldefined by case 12 and cover 18 of the battery 10. In another fillportembodiment, a filltube is located on case 12 or cover 18. After theelectrolyte is injected into battery 10, the filltube is crimped shutand welded. This embodiment eliminates the “press-fit” operation. Inanother embodiment, a plug or button is welded over or into an open portwhere the electrolyte is injected. This embodiment eliminates aredundant seal. In yet another embodiment, a gasket seal or epoxy isutilized to plug an open port.

With reference to FIG. 7, the details regarding construction ofelectrode assembly 14, such as connector tabs, electrode pouches, etc.,are secondary to the present invention and will be described generallybelow with a more complete discussion being found in, e.g., U.S. Pat.No. 5,458,997 (Crespi et al.). With reference to FIG. 7, electrodeassembly 14 is preferably a wound or coiled structure similar to thosedisclosed in, e.g., U.S. Pat. No. 5,486,215 (Kelm et al.) and U.S. Pat.No. 5,549,717 (Takeuchi et al.). However, electrode assembly 14 could bea folded or stacked electrode assembly structure. The composition of theelectrode assemblies can vary, although one preferred electrode assemblyincludes a wound core of lithium/CSVO. Other battery chemistries arealso anticipated, such as those described in U.S. Pat. No. 5,616,429 toKlementowski and U.S. Pat. No. 5,458,997 to Crespi et al., with thepreferred cores comprising wound electrodes. Such a design provides avolumetrically efficient battery useful in many different implantabledevices.

Electrode assembly 14 preferably includes an anode, a cathode, cathodeconnector tabs 40, anode connector tab 41, and a porous, electricallynon-conductive separator material encapsulating either or both of theanode and cathode. These three components are wound to form electrodeassembly 14. The anode portion of the electrode assembly can comprise anumber of different materials including an anode active material locatedon an anode conductor element. Examples of suitable anode activematerials include, but are not limited to: alkali metals, materialsselected from Group IA of the Periodic Table of Elements, includinglithium, sodium, potassium, etc., and their alloys and intermetalliccompounds including, e.g., Li—Si, Li—B, and Li—Si—B alloys andintermetallic compounds, insertion or intercalation materials such ascarbon, or tin-oxide. Examples of suitable materials for the anodeconductor element include, but are not limited to: stainless steel,nickel, titanium, or aluminum. However, in a preferred embodiment theanode is comprised of lithium with a titanium conductor.

The cathode portion of the electrode assembly preferably includes acathode active material located on a cathode current collector that alsoconducts the flow of electrons between the cathode active material andthe cathode terminals of electrode assembly 14. Examples of materialssuitable for use as the cathode active material include, but are notlimited to: a metal oxide, a mixed metal oxide, a metal sulfide orcarbonaceous compounds, and combinations thereof. Suitable cathodeactive materials include silver vanadium oxide (SVO), copper vanadiumoxide, combination silver vanadium oxide (CSVO), manganese dioxide,titanium disulfide, copper oxide, copper sulfide, iron sulfide, irondisulfide, carbon and fluorinated carbon, and mixtures thereof,including lithiated oxides of metals such as manganese, cobalt, andnickel. However, in a preferred embodiment the cathode is comprised ofCSVO with a titanium conductor.

Preferably, the cathode active material comprises a mixed metal oxideformed by chemical addition, reaction or otherwise intimate contact orby thermal spray coating process of various metal sulfides, metal oxidesor metal oxide/elemental metal combinations. The materials therebyproduced contain metals and oxides of Groups IB, IIB, IIIB, IVB, VB,VIB, VIIB, and VIII of the Periodic Table of Elements, which includesnoble metals and/or their oxide compounds.

The cathode active materials can be provided in a binder material suchas a fluoro-resin powder, preferably polytetrafluoroethylene (PTFE)powder that also includes another electrically conductive material suchas graphite powder, acetylene black powder, and carbon black powder. Insome cases, however, no binder or other conductive material is requiredfor the cathode.

The separator material should electrically insulate the anode from thecathode. The material is preferably wettable by the cell electrolyte,sufficiently porous to allow the electrolyte to flow through theseparator material, and maintain physical and chemical integrity withinthe cell during operation. Examples of suitable separator materialsinclude, but are not limited to: polyethylenetetrafluoroethylene,ceramics, non-woven glass, glass fiber material, polypropylene, andpolyethylene.

As best seen in FIG. 1, an insulator cup 16 is used to electricallyisolate electrode assembly 14 from battery cover 18. With reference toFIG. 8, an insulator cup embodiment of the present invention is shown.Insulator cup 16 includes slits 44, 46, and 48 to accommodate connectortabs 40 and anode tab 41. Preferably insulator cup 16 is comprised ofETFE with a thickness of 0.030 cm. (0.012 inches), however, it iscontemplated that other thicknesses and materials could be used such asHDDE, polypropylene, polyurethane, fluoropolymers, and the like.Insulator cup 16 performs several functions including working inconjunction with battery case liner 31 to isolate battery case 12 andbattery cover 18 from electrode assembly 14. It also provides mechanicalstability for electrode assembly 14. In addition, it serves to hold thecoil assembly together which substantially aids in the manufacturing ofbattery 10. Since electrode assembly 14 is preferably a wound coil,insulator cup 16 also helps prevent assembly 14 from unwinding.Insulator cup 16 further provides protection for assembly 14 duringhandling and during the life of assembly 14. Finally, and mostimportantly cup 16 provides a thermal barrier between assembly 14 andcover 18 during the laser welding procedure that joins cover 18 withcase 12, which is discussed in more detail below.

As stated above in detail, case 12 and cover 18 are preferably weldedtogether to provide a hermetic enclosure for electrode assembly 14.However, because of the battery's structure, the weld is performedwithin 1 mm of electrode assembly 14. Since, case 12 and cover 18 arefirst assembled before the welding process, a finite gap between case 12and cover 18 typically exists. However, any time there is a finite gapthere is the possibility that the laser beam utilized in the laserwelding process may penetrate battery 10 and damage electrode assembly14. Therefore, molded insulator cup 16 is preferably comprised of ETFEand further is preferably compounded or mixed with carbon black,although cup 16 may be simply coated with carbon black in lieu of theforegoing. The carbon coloring serves to make the insulator black. Theblack color serves to shield electrode assembly 14 from laser beampenetration into battery 10. Essentially cup 16 is opaque to the laserwavelength, which is approximately 1 micron. Alternatively, this thermalprotection could be accomplished with a metal ring compatible with case12 and cover 18, such as titanium, stainless steel, niobium, etc.,however, preferably cup 16 is an opaque polymer as discussed above.

With reference to FIGS. 9 and 10, a top and side profile of a batterycover with a feedthrough assembly is shown. Battery cover 18 iscomprised of an electrode assembly region 60, a headspace region 62, anda feedthrough aperture 64. Similar to battery case 12, battery cover 18is comprised of medical grade titanium to provide a strong and reliableweld creating a hermetic seal with the battery case. However, it iscontemplated that battery cover 18 could be made of any type of materialas long as the material was electrochemically compatible. Battery cover18 is designed to fit overtop the shallow opening 29 within lip 27 onthe perimeter of opening 29. Therefore battery cover 18 rests on thesmall lip, substantially flush with the top of opening 29 which providesfor substantial ease of manufacturing when battery cover 18 is laserwelded to battery case 12.

Feedthrough aperture 64 is tapered outwardly not only to allowfeedthrough assembly 24 to rest within aperture 64, but also to providean isolation buffer between glass member 72 and the weld which willattach feedthrough assembly 24 to battery cover 18. With reference toFIG. 11, an embodiment for the feedthrough assembly is shown.Feedthrough assembly 24 is comprised of feedthrough pin 70, glasssealing member 72, ferrule 74, flange 76, and retention slots 78. As isshown in the figure, ferrule 74 is tapered at a substantially equalangle as the tapers on feedthrough aperture 64 so that it may bereceived within aperture 64. This tapered portion of ferrule 74 is alsothe location where the weld to join feedthrough assembly 24 to batterycover 18 occurs. The taper of ferrule 74 not only places the weldfurther from glass member 72, but also creates more surface area inwhich to dissipate the heat from the weld. As is discussed above,feedthrough aperture 64 and assembly 24 can be located anywhere on case12 or cover 18.

Feedthrough pin 70 is preferably comprised of niobium, however, anyconductive material could be utilized without departing from the spiritof the invention. Niobium is preferably chosen for its low resistivity,its material compatibility during welding with titanium, and itscoefficient of expansion when heated. As will be discussed in moredetail below, pin 70 is preferably welded to coupling 20 (FIG. 12) andto connector module 100 (FIG. 17) located outside of battery 10.Coupling 20 and contacts 114 and 116 on connector module 100 arepreferably made of niobium and titanium respectively. Niobium andtitanium are compatible metals, meaning that when they are weldedtogether a strong reliable weld is created. Pin 70 has a diameter of0.055 cm. (0.0216 inches), preferably selected for a high currentapplication. Glass sealing member 72 is comprised of CABAL-12(calcium-boro-aluminate) glass, which provides electrical isolation offeedthrough pin 70 from battery cover 18. The pin material is in partselected for its suitability in feedthrough assembly 24 for its abilityto join with glass sealing member 72, which results in a hermetic seal.

CABAL-12 is very corrosion resistant as well as being a good insulator.Therefore, CABAL-12 provides for good insulation between pin 70 andbattery cover 18 as well as being resistant to the corrosive effects ofthe electrolyte. Preferably glass member 72 provides an electricalinsulation resistance of 1000 M-ohms from pin 70 to ferrule 74 at 100VDC per Mil-STD 202F method 302. Glass member 72 is then preferablyplaced within a conduit on ferrule 74 having a diameter of 0.060 inches.Preferably glass member 72 provides a hermetic seal both with pin 70 andferrule 74 having a leak rate not exceeding 10⁻⁸ ATM STD cc/sec ofhelium per MIL-STD 202F method 112E. Ferrule 74 is preferably comprisedof medical grade titanium that is annealed according to ASTM F67.Although, preferable materials have been listed for the componentslisted above, it is contemplated that other materials could be utilized.Feedthrough pin 70, sealing member 72, and ferrule 74 are heatedtogether to allow the glass to melt and reform to seal within ferrule 74and around pin 70.

After pin 70, glass member 72, and ferrule 74 are placed together; thebottom of ferrule 74 is subjected to an overmolding process where it iscoated with polypropylene to provide electrical insulation between pin70 and ferrule 74. The polypropylene overmold helps prevent pin 70 frombeing bent over to touch ferrule 74 thus creating an electrical short.The overmolding also provides mechanical short protection for othersituations, such as pin 70 bending to bridge to connector tabs 40 and41. Further, the polypropylene coating limits the amount of electrolyteexposure to glass member 72. It is contemplated that other insulationmaterials could be used as a coating such as PETFE (polyethylene tetrafluoro ethylene), ETFE (ethylene tetrafluorethylene), polyurethane,polyethylene, and the like. The polypropylene molding is held in placeby retention slots 78, which act to prevent the molding from twistingoff or pulling away from feedthrough assembly 24. Further, during theovermolding process flange 76 is created. Flange 76 provides a retentionmeans for headspace insulator 22 (FIG. 14), which is discussed in moredetail below. Preferably flange 76 has a thick plastic-thinplastic-thick plastic design, which allows for insulator 22 to besnapped onto flange 22.

In another embodiment, the overmolding is extended out over a plate withslots for cathode tabs 40. Tabs 40 are then welded to the plate, whichin turn is welded to feedthrough pin 70. This embodiment provides arelatively rigid system, which has advantages of preventing insulatorsfrom inadvertently folding or collapsing out of place.

With reference to FIG. 12, an embodiment showing the interconnectionbetween a feedthrough pin and a coupling is shown. As is shown, coupling20 is welded to cathode tabs 40 while anode tab 41 is in contact withbattery cover 18. Coupling 20 is preferably comprised of niobium with adiameter of 0.055 cm. (0.0216 inches), which is compatible with pin 70.Coupling 20 is welded to feedthrough pin 70 to provide an electricalconnection between the cathode of electrode assembly 14 and theimplantable medical device. While for the purposes of this discussioncoupling 20 is welded to cathode tabs 40 and feedthrough pin 70, it iscontemplated that an alternate method of attachment may be utilized suchas soldering, electrically conductive glue, or an electricallyconductive thermoset material and the like, without departing from thespirit of the invention. At the time of the present invention, however,the inventors have found that welding provides the most reliableconnection. Coupling 20 allows for ease in manufacturing by eliminatingthe need to bend tabs 40 or pin 70 to reach a coupling between them.Since coupling 20 has a “U” shape it allows for more compliance inaligning with the position of tabs 40 and pin 70.

What is further shown with reference to FIG. 12 is that the headspacevolume is substantially reduced when compared with prior implantablemedical device batteries as shown in FIG. 13 and as discussed above.

With respect to FIG. 14, a headspace insulator is shown. Preferablyheadspace insulator 22 is comprised of polypropylene, however, otherinsulative materials are contemplated. Headspace insulator 22 preferablycovers coupling 20 and cathode tabs 40. Insulator 22 is designed toprovide mechanical line of sight insulation and electrical protectionfrom electrical shorts. Insulator 22 also prevents any materials fromcontacting cathode tabs 40 and coupling 20, which could compromise thebattery's operation. With reference to FIG. 15, which shows a rearprofile view of the headspace insulation, slot 90 is shown, which snapsonto flange 76 of feedthrough assembly 24. This connection holdsinsulator 22 into place and protects cathode tabs 40 and coupling 20during handling and discharge.

With reference to FIG. 16, a battery assembly with insulators and abattery connector is shown. Upon battery 10 being mechanically assembledas described in detail above, a battery connector 100 is connected topin 70, which is described in more detail below. Connector 100 isutilized to route the energy from battery 10 to the implantable medicaldevice. In an implantable cardioverter defibrillator the energy would betransferred to a switching system such as that described in U.S. Pat.No. 5,470,341 (Kuehn et al.). Battery insulators 104 and 106 are held inplace on battery 10 with two pressure sensitive acrylic adhesive strips102. These strips are similar to double back adhesive tape, which istacky on both sides of the tape. While pressure sensitive acrylic isdiscussed for purposes of the embodiment, it is fully contemplated thatother methods of attachment for insulators 104 and 106 could be utilizedwithout departing from the spirit of the invention.

Insulators 104 and 106 are preferably comprised of a thermoplasticpolyimide film, however, other insulator materials are contemplated.Insulators 104 and 106 provide electrical and mechanical insulation forbattery 10. Since battery case 12 and cover 18 are negatively charged,they need to be electrically isolated from the rest of the implantablemedical device. Further, insulators 104 and 106 provide mechanicalinsulation by protecting battery 10 during handling and thermalprotection when the implantable device shields are welded together,which is outside the scope of the present invention.

With reference to FIG. 17, a battery connector is shown. Connector 100is comprised of a main body 110, a base 112, a positive contact 114, anda negative contact 116. Main body 110 provides a housing for base 112,positive contact 114, and negative contact 116 and is preferablycomprised of polyetherimide, however other insulator materials arecontemplated. Body 110 also acts as an insulator to electrically isolatepositive contact 114 from negative contact 116. Base 112, positivecontact 114, and negative contact 116 are preferably comprised oftitanium, however other materials are contemplated. Connector 100 isplaced over top of pin 70 in which pin 70 is received by an aperture inpositive contact 114. Pin 70 is then preferably laser welded to positivecontact 114 as well as base 112 which is laser welded to cover 18. Whatcannot be shown with reference to FIG. 17 is that negative contact 116is in contact with base 112. Thus after the laser welding is completethere exists a positive charge on contact 114 and a negative charge oncontact 116. Positive contact 114 and negative contact 116 are thenribbon bonded, as is known in the art, to the implantable medicaldevice's circuitry. It is of note that connector 100 is the only exposedportion of battery 10 after it is received through triangular cut 108 asshown in FIG. 15. It is further noted that an alternative embodimentwould include a negative charge on contact 114 and a positive charge oncontact 116.

It will be appreciated that the present invention can take many formsand embodiments. The true essence and spirit of this invention aredefined in the appended claims, and it is not intended that theembodiments of the invention presented herein (i.e., described and/orillustrated) should limit the scope thereof.

What is claimed is:
 1. An electrochemical cell comprising an insulator,wherein the electrochemical cell comprises a cell housing joinable to acell cover, the insulator comprising: a case having a bottom, an opentop to receive an electrode assembly, and at least one side extendingfrom said bottom; and said insulator being opaque to a laser beam.
 2. Anelectrochemical cell according to claim 1 comprising slots to receive atleast one cathode tab and at least one anode tab.
 3. An electrochemicalcell according to claim 2, wherein the slots are located on the at leastone side.
 4. An electrochemical cell according to claim 1, wherein thecase bottom is adjacent to the cell cover and provides an electricalbarrier between the electrode assembly and the cell cover.
 5. Anelectrochemical cell according to claim 4, wherein the electrodeassembly is up to five millimeters from a weld joint joining the cellcover with the cell housing.
 6. An electrochemical cell according toclaim 5, wherein the case provides a thermal barrier between the weldjoint and the electrode assembly.
 7. An electrochemical cell accordingto claim 6, wherein the case provides a radiation barrier between thelaser beam and the electrode assembly.
 8. An electrochemical cellaccording to claim 1, wherein 20 the case is comprised of a materialselected from the group consisting of HDPE, polypropylene, polyurethane,and fluoropolymers.
 9. An electrochemical cell according to claim 1,wherein the case is comprised of ETFE.
 10. An electrochemical cellaccording to claim 9, wherein the case is comprised of ETFE comprising ablack resin.
 11. An electrochemical cell according to claim 10, whereinthe carbon resin provides the laser beam opacity.
 12. An implantablemedical device including a battery, the battery comprising: means forproviding a shallow battery case having an open end, a base locatedopposite the open end, and a plurality of sides being radiused atintersections with each other and the base; means for providing aninsulator having a bottom, an open top to receive the electrodeassembly, and at least one side extending from said bottom; saidinsulator being opaque to a laser beam; means for inserting an electrodeassembly into the insulator; means for placing a cover over the open endof the case, and hermetically sealing the cover to the case; and meansfor placing an electrolyte inside the battery housing.
 13. A deviceaccording to claim 12 wherein the insulator is comprised of slots toreceive at least one cathode tab and at least one anode tab.
 14. Adevice according to claim 13, wherein the slots in the insulator arelocated on the at least one side.
 15. A device according to claim 12,wherein the insulator bottom is adjacent to the cover and provides anelectrical barrier between the electrode assembly and the cover.
 16. Adevice according to claim 15, wherein the electrode assembly is up to 5mm from a weld joint creating the hermetic seal.
 17. A device accordingto claim 16, wherein the insulator provides a thermal barrier betweenthe weld joint and the electrode assembly.
 18. A device according toclaim 17, wherein the insulator provides a radiation barrier between alaser beam and the electrode assembly.